To ensure that the rear wheels of a motor vehicle will not lock sooner than the front wheels, it is common practice to distribute the brake forces among the axles of the vehicle in such a way that the braking effect is more fully utilized at the front axle than at the rear axle. This arrangement affords good directional stability during braking. On the other hand, this has the disadvantage that the maximum physically possible vehicle deceleration is not attained because, at least part of the time, a lower braking force is applied by way of the rear wheels than would otherwise be possible. These design criteria have been reflected in statutory provisions.
Because of this brake force distribution even in motor vehicles equipped with brake slip regulating means (i.e., antilocking or antiskid systems) for all wheels or all axles of the vehicle, brake slip regulation will generally commence first at the front axle of the vehicle. In fact, such slip regulation occurs at a time when the maximum possible brake forces have not yet been attained at the rear axle. In many cases, therefore, even in motor vehicles with brake slip regulation, the maximum possible vehicle deceleration is not achieved. It will be achieved only in those special cases where the operator deliberately increases the brake system pressure to such an extent that, although brake slip regulation has commenced at the front axle, the maximum possible brake force, or the forces sufficient to cause brake slip regulation, will also be applied at the rear axle.
The object of the invention is to provide an improved pressure-actuated brake system in vehicles having brake slip regulation including sensors to monitor the braking condition at each wheel so as to avoid brake locking which is arranged so that the vehicle deceleration will be increased upon braking and commencement of brake slip regulation on only some of the wheels.